In a corporate environment where you care about such things, you really want to disable the functionality of the user setting the background in the operating system, not in a specific application. Otherwise, you’re going to have to track down every application that includes this functionality, figure out how to disable it it in that application, and find a way to apply that change to every PC. (Microsoft’s Photos app, for example, can set pictures as either background or lock screen.)
Just checked, it’s there on Firefox on Windows, too. Also, Windows itself has a “Send To…” item on the right click menu for images, and one of the options in the submenu below that is “Mail Recipient”. (Chrome has the possibly-even-more-useless “Generate QR code for this image” but I don’t see an “e-mail this image” option in Chrome on Windows.)